Electrolysis Flashcards
What is an electrolyte?
- An ionic compound in its molten or aqueous state.
- Aqueous - dissolved in water.
Why can an electrolyte carry charge?
An ionic compound in is molten or aqueous state has mobile ions which can carry charge.
What is electrolysis?
A process which uses electrical energy (from a direct current supply) to decompose electrolytes.
What is the cathode and anode?
- Cathode - negative electrode
- Anode - positive electrode
Where do charged ions in the electrolyte move to during electrolysis?
- Cations (positive ions) move towards the cathode (negative electrode).
- Anions (negative ions) move towards the anode (positive electrode).
What happens at the anode during electrolysis?
The anions (negatively charged ions) lose electrons to form their elements.
What happens at the cathode during electrolysis?
Cations (positively charged ions) gain electrons to form their elements.
Name the processes that occur at each electrode during electrolysis
- Anode (positive) - oxidation
- Cathode (negative) - reduction.
What is formed at each electrode in electrolysis?
- Positive electrode: Non metal
- Negative electrode: Metal or hydrogen
How can you predict whether a metal or hydrogen will form at the negative electrode?
If hydrogen is above the metal in the reactivity series then the metal will form. If the metal is more reactive than hydrogen then hydrogen will form.
What is formed at each electrode during the electrolysis of copper chloride solution?
- Positive electrode: Chlorine
- Negative electrode: Copper
What is formed at each electrode during the electrolysis of sodium sulfate solution?
- Positive electrode: Oxygen
- Negative electrode: Hydrogen
What is formed at each electrode during the electrolysis of molten lead bromide?
- Positive electrode: Bromine
- Negative electrode: Hydrogen
Predict what will be formed at each electrode during the electrolysis of molten zinc chloride
- Positive electrode: Chlorine
- Negative electrode: Zinc
What is formed at each electrode during the electrolysis of sodium chloride solution?
- Positive electrode: Chlorine
- Negative electrode: Hydrogen
What is formed at each electrode during the electrolysis of water acidified with sulfuric acid?
- Positive electrode: Oxygen
- Negative electrode: Hydrogen
What are the half equations for the reactions occuring at the cathode and anode during the electrolysis of copper chloride?
- Anode: 2Cl- → Cl2 + 2e-
- Cathode: Cu2++ 2e- → Cu
What does oxidation mean in terms of electrons?
Loss of electrons
What does reduction mean in terms of electrons?
Gain of electrons
Describe how electrolysis of copper sulfate can be used to purify copper
- Place 2 copper electrodes into copper sulfate solution. The anode should be impure copper and cathode should be pure copper. Connect to a power supply.
- The copper in the impure anode is pulled towards the cathode to form pure copper. Impurities form as sludge below the anode. Cu2+ ions from copper sulfate remain in solution.
